WASHINGTON, Feb 14 (Reuters) - More than half the U.S.diplomatic posts overseas may not fully meet security standards,a senior U.S. official told a hearing on Thursday that followsan attack on the mission in Benghazi in which the U.S.ambassador and three other Americans died.

Pat Kennedy, the under secretary of state for management atthe State Department, told a House of Representativesappropriations subcommittee that the United States had adiplomatic presence at 283 locations around the world.

He said 97 safe and secure facilities had been completedsince the 1999 passage of a U.S. law authorizing additionalfunding for security upgrades, including 70 full replacements of embassies or consulates, as well as some building of Marineguard quarters and office annexes.

"There remain approximately 158 posts that have facilitiesthat may not fully meet current security standards," he said.

"Many of these facilities were built or acquired prior tothe establishment of the current security standards, and othersare subject to authorized waivers and/or exceptions."

Kennedy was giving written testimony at a closed hearing ofthe subcommittee that oversees the State Department, but hiscomments were posted afterwards on a House website.

The issue of embassy security has been under particularscrutiny since the Sept. 11, 2012 Benghazi attack. In December,an independent review described security precautions at the U.S.mission in the eastern Libyan city as "grossly inadequate todeal with the attack that took place" there.

Another State Department official said a variety of factors,including increased costs of fuel and construction, contributedto the delay in upgrading security for diplomatic posts.

"To accommodate our building requirements, collocate staff,and achieve required setback (from the property perimeter), weseek sites of about 7 to 10 acres of buildable land. These canbe challenging to find in a capital city," the official toldReuters.

One of the lawmakers who attended the hearing said part ofthe problem was that many posts are located directly on streets.This makes them more vulnerable to car bombs and other attacks.

"The problem is, there are a good number of our embassiesthat are right at the street," Representative Nita Lowey, thepanel's ranking Democrat, told Reuters. "So ideally, you'd wantto find new land to move them. So they are looking at all kindsof different methods."

BOMBINGS SPURRED SECURITY UPGRADES

The 1999 law on embassy security construction was passedafter the deadly bombings of the U.S. embassies in Kenya andTanzania a year earlier in which hundreds of people were killed.

In addition to providing funding for security upgrades, the1999 law contained some new security requirements, including amandate that any new embassy or consulate building be no lessthan 100 feet (30 meters) from the compound's perimeter.

Kennedy said Congress had appropriated about $10 billion forthe embassy security construction effort since 1999, and that 37projects were currently in design or construction.

Following the Benghazi attack, the State Department asked inDecember for more than $1 billion to be reprogrammed in thecurrent fiscal year to improve security at diplomatic missions.

The Senate recently approved the transfer of $1.1 billion infunds that are no longer needed in Iraq because of reducedoperations there.

The House has yet to decide whether to make thereprogramming move, although Representative Kay Granger, thechair of the House appropriations subcommittee, told Reuters shelooked favorably on the idea.

"There is great concern, as you can imagine, about whatneeds to be done," said Granger, a Republican.

The issue is likely to get caught up in congressionalwrangling over the overall budget for this year as well asautomatic spending cuts set for March 1.